Conserved Processes and Lineage-Specific Proteins in Fungal Cell Wall Evolution

Department of Biological Sciences and Center for Gene Structure and Function, and Computer Science, Hunter College, City University of New York, New York, NY 10021, USA; Department of Biology, Brooklyn College of City University of New York, Brooklyn, NY, 11210, USA

^* To whom correspondence should be addressed. Email: plipke{at}brooklyn.cuny.edu.

	Abstract

The cell wall is a defining organelle that differentiates fungi from its sister clades in the opisthokont superkingdom. With a sensitive technique to align low-complexity protein sequences, we have identified 187 cell wall-related proteins in Saccharomyces cerevisiae, and determined the presence or absence of homologs in 17 other fungal genomes. There were both conserved and lineage-specific cell wall proteins, and the degree of conservation was strongly correlated with protein function. Some functional classes were poorly conserved and lineage-specific: adhesins, structural wall glycoprotein components, and un-annotated ORFs. These proteins are primarily those that are constituents of the walls themselves. On the other hand, glycosyl hydrolases and transferases, proteases, lipases, proteins in the glycosyl phosphatidyl-inositol-protein synthesis pathway, and chaperones were strongly conserved. Many of these proteins are also conserved in other eukaryotes and are associated with wall synthesis in plants. This gene conservation, along with known similarities in wall architecture, implies that the basic architecture of fungal walls is ancestral to the divergence of the ascomycetes and basidiomycetes. The contrasting lineage-specificity of wall-resident proteins implies diversification. Therefore, fungal cell walls consist of rapidly diversifying proteins that are assembled by the products of an ancestral and conserved set of genes.